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Message-ID: <e19b9dcc-99d0-414d-95ef-69149daedaa9@embeddedor.com>
Date: Tue, 24 Oct 2023 19:06:58 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kalle Valo <kvalo@...nel.org>,
Jeff Johnson <quic_jjohnson@...cinc.com>,
Manikanta Pubbisetty <quic_mpubbise@...cinc.com>
Cc: ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-hardening@...r.kernel.org
Subject: Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on
this, please :)
[+CC Manikanta Pubbisetty ]
As Johannes[1] pointed out, this `memset()` is probably unnecessary:
./drivers/net/wireless/ath/ath10k/wmi.c:
8920 memset(skb->data, 0, sizeof(*cmd));
However, the same exact issue[2] is present at the line below inside
function `ath10k_wmi_alloc_skb()`:
drivers/net/wireless/ath/ath10k/wmi.c:
1799 memset(skb->data, 0, round_len);
Thanks
--
Gustavo
[1] https://lore.kernel.org/linux-hardening/26b15f4702cef17fe70b496a62f03735874bd16a.camel@sipsolutions.net/
[2] https://lore.kernel.org/linux-hardening/07e9bb04-f9fc-46d5-bfb9-a00a63a707c0@embeddedor.com/
On 10/24/23 13:50, Gustavo A. R. Silva wrote:
> Hi all,
>
> While working on tranforming one-element array `peer_chan_list` in
> `struct wmi_tdls_peer_capabilities` into a flex-array member
>
> 7187 struct wmi_tdls_peer_capabilities {
> ...
> 7199 struct wmi_channel peer_chan_list[1];
> 7200 } __packed;
>
> the following line caught my attention:
>
> ./drivers/net/wireless/ath/ath10k/wmi.c:
> 8920 memset(skb->data, 0, sizeof(*cmd));
>
> Notice that before the flex-array transformation, we are zeroing 128
> bytes in `skb->data` because `sizeof(*cmd) == 128`, see below:
>
> $ pahole -C wmi_10_4_tdls_peer_update_cmd drivers/net/wireless/ath/ath10k/wmi.o
> struct wmi_10_4_tdls_peer_update_cmd {
> __le32 vdev_id; /* 0 4 */
> struct wmi_mac_addr peer_macaddr; /* 4 8 */
> __le32 peer_state; /* 12 4 */
> __le32 reserved[4]; /* 16 16 */
> struct wmi_tdls_peer_capabilities peer_capab; /* 32 96 */
>
> /* size: 128, cachelines: 2, members: 5 */
> };
>
> So, after the flex-array transformation (and the necessary adjustments
> to a few other lines of code) we would be zeroing 104 bytes in
> `skb->data` because `sizeof(*cmd) == 104`, see below:
>
> $ pahole -C wmi_10_4_tdls_peer_update_cmd drivers/net/wireless/ath/ath10k/wmi.o
> struct wmi_10_4_tdls_peer_update_cmd {
> __le32 vdev_id; /* 0 4 */
> struct wmi_mac_addr peer_macaddr; /* 4 8 */
> __le32 peer_state; /* 12 4 */
> __le32 reserved[4]; /* 16 16 */
> struct wmi_tdls_peer_capabilities peer_capab; /* 32 72 */
>
> /* size: 104, cachelines: 2, members: 5 */
> /* last cacheline: 40 bytes */
> };
>
> This difference arises because the size of the element type for the
> `peer_chan_list` array, which is `sizeof(struct wmi_channel) == 24 `
>
> $ pahole -C wmi_channel drivers/net/wireless/ath/ath10k/wmi.o
> struct wmi_channel {
> __le32 mhz; /* 0 4 */
> __le32 band_center_freq1; /* 4 4 */
> __le32 band_center_freq2; /* 8 4 */
>
> [..]
> /* 20 4 */
>
> /* size: 24, cachelines: 1, members: 6 */
> /* last cacheline: 24 bytes */
> };
>
> is included in `sizeof(*cmd)` before the transformation.
>
> So, my question is: do we really need to zero out those extra 24 bytes in
> `skb->data`? or is it rather a bug in the original code?
>
> Thanks!
> --
> Gustavo
>
>
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